Patients who suffer from the pain and immobility caused by osteoarthritis and rheumatoid arthritis have an option of joint replacement surgery. Joint replacement surgery is quite common and enables many individuals to function properly when it would not be otherwise possible to do so. Artificial joints are usually comprised of metal, ceramic and/or plastic components that are fixed to existing bone.
Such joint replacement surgery is otherwise known as joint arthroplasty. Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged joint is replaced with a prosthetic joint. In a typical total joint arthroplasty, the ends or distal portions of the bones adjacent to the joint are resected or a portion of the distal part of the bone is removed and the artificial joint is secured thereto.
There are known to exist many designs and methods for manufacturing implantable articles, such as bone prostheses. Such bone prostheses include components of artificial joints such as elbows, hips, knees and shoulders.
Currently in total hip arthroplasty, a major critical concern is the instability of the joint. Instability is associated with dislocation. Dislocation is particularly a problem in total hip arthroplasty.
Factors related to dislocation include surgical technique, implant design, implant positioning and patient related factors. In total hip arthroplasty, implant systems address this concern by offering a series of products with a range of lateral offsets, neck offsets, head offsets and leg lengths. The combination of these four factors affects the laxity of the soft tissue. By optimizing the biomechanics, the surgeon can provide a patient a stable hip much more resistant to dislocation.
In order to accommodate the range of patient arthropathy metrics, a wide range of hip implant geometries are currently manufactured by DePuy Orthopaedics, Inc., the assignee of the current application, and by other companies. In particular, the S-ROM® total hip systems offered by DePuy Orthopaedics, Inc. include three offsets, three neck lengths, four head lengths and one leg length adjustment. The combination of all these biomechanic options is rather complex.
Anteversion of a total hip system is closely linked to the stability of the joint. Improper anteversion can lead to dislocation and patient dissatisfaction. Anteversion control is important in all hip stems. However, it is a more challenging issue with the advent of stems with additional modularity.
The prior art has provided for some addressing of the anteversion problem. For example, the current S-ROM® stems have laser markings on the medial stem and the proximal sleeve. This marking enables the surgeon to measure relative alignment between these components. Since the sleeve has infinite anteversion, it is not necessarily oriented relative to a bony landmark that can be used to define anteversion. In fact, the current sleeves are sometimes oriented with the spout pointing directly laterally into the remaining available bone.
When a primary or index total joint arthroplasty fails, a revision procedure is performed in which the index devices (some or all) are removed. Quite often the remaining bone is significantly compromised compared to a primary hip procedure. Significant bone loss is observed, often with a lack of bone landmarks typically used for alignment.
In a common step in the surgical procedure known as total hip arthroplasty, a trial or substitute stem is first implanted into the patient. The trial is utilized to verify the selected size and shape of the implant in situ on the patient and the patient is subjected to what is known as a trial reduction. This trial reduction represents moving the joint, including the trial implant through selected typical motions for that joint. Current hip instruments provide a series of trials of different sizes to help the surgeon assess the fit and position of the implant. Trials, which are also known as provisionals, allow the surgeon to perform a trial reduction to assess the suitability of the implant and the implant's stability prior to final implant selection. In order to reduce inventory costs and complexity, many trialing systems are modular. For example, in the Excel™ Instrument System, a product of DePuy Orthopaedics, Inc., there is a series of broaches and a series of neck trials that can be mixed and matched to represent the full range of implants. There is a single fixed relationship between a broach and a neck trial, because these trials represent a system of monolithic stem implants.
Likewise, in the current S-ROM® instrument systems provided by DePuy Orthopaedics, Inc., there are neck trials, proximal body trials, distal stem trials, head trials and sleeve trials. By combining all of these components, the implant is represented. Since the S-ROM® stem is modular and includes a stem and a sleeve, the angular relationship or relative anteversion between the neck and the sleeve is independent and represented by teeth mating between the neck and the proximal body trial. The proximal body trial has fixed transverse bolts that are keyed to the sleeve in the trialing for straight, primary stems. The long stem trials do not have the transverse bolts and are thus not rotationally stable during trial reduction and therefore are not always used by the surgeon.
With the introduction of additional implant modularity, the need for independent positioning of the distal stem, proximal body and any sleeve that comprise the implants is required. Currently bowed, monolithic stems are offered with a fixed amount of anteversion, typically 15 degrees.
Currently available implants, trials and instruments result in a lengthy surgical procedure. This lengthy surgical procedure includes the steps of preparing the canal, removing the instruments to prepare the canal, implanting trials, performing a trial reduction and then implanting the prosthesis. This lengthy procedure increases the risk of the patient's surgical complications.
When utilizing currently available instruments, trials and surgical procedures, the surgeon must perform the trial reduction on the patient before the surgeon has any feedback regarding the appropriateness of the trial and the positioning of the trial in the body. Adjustments in the positioning and selection of the trial and resultant implants thus become difficult and time consuming to perform.
Utilizing the current instruments, the trials and implants all need to be properly located and selected to obtain the optimum results for the patient. The positioning of the trial with respect to the femur and the implant with respect to the trial currently allow for much variation from procedure to procedure.
To optimize patient outcomes, orthopaedic surgery preferably conserves as much of the resected bone as possible. Current surgical procedures require that sufficient bone be resected and removed by instruments in the proximal bone to provide for clearance for the proximal trial and the proximal implant. Thus, under current techniques, material must be removed proximally on the bone to provide for the variety of positions that may be optimum for the patient.
US Patent Application Publication No. 20040122439 entitled “ADJUSTABLE BIOMECHANICAL TEMPLATING & RESECTION INSTRUMENT AND ASSOCIATED METHOD”, US Patent Application Publication No. 20040122437 entitled “ALIGNMENT DEVICE FOR MODULAR IMPLANTS AND METHOD” and US Patent Application Publication No. 20040122440 entitled “INSTRUMENT AND ASSOCIATED METHOD OF TRIALING FOR MODULAR HIP STEMS” are hereby incorporated in their entireties by reference.
When performing hip arthroplasty using bowed stems, the distal canal is prepared with a reamer and the bowed step is installed in the reamed cavity. The longitudinal centerline of the proximal body of the implant is not in alignment with the centerline of the distal stem due to the fact that the distal stem is bowed. The reamer that prepares the distal cavity can not remove bone to provide clearance to the proximal body in a precise manner to minimize bone removal, due to the fact that the proximal body centerline of the implant is not in alignment with the distal stem centerline. Either additional material must be removed by the distal reamer from the proximal bone to allow for this non-alignment, or additional material must be removed by other means, for example by an osteotome. Either method requires additional bone removal that is not clinically desired.
While the prior art has attempted to reduce the steps in surgical techniques and improve the ability to precisely remove bone to prepare the bone for receiving a proximal component, the need remains for a system and apparatus to reduce the steps in surgical techniques utilizing distal reamers and proximal bodies for modular implants.
The present invention is directed to alleviate at least some of the problems with the prior art.